Embodiments of the invention relate to a pump arrangement and, in particular, to a pump arrangement comprising a safety valve at a pump outlet of a pump.
Diaphragm pumps comprising passive check valves at the pump inlet and the pump outlet are exemplarily known from DE-A-19719862. Peristaltic pumps comprising no active valve are exemplarily known from DE-A-10238600. In particular, the above documents disclose micropumps, which are taken as such pumps the pump volume of which when being actuated once are in a range of microliters or below.
Known micropumps are problematic in that free flow through the pumps may take place when an overpressure or positive pressure is applied to the inlet reservoir which is connected to the respective pump inlet, and there is no operating voltage applied to the pump.
Normally closed self-blocking valves are known from DE-A1-10048376 and WO-A1-2004/081390. A normally closed valve is to be taken as a valve which is closed when unactuated.
DE-A1-10048376 discloses a normally closed self-blocking valve in which a positive pressure at a valve inlet has a closing effect. The valve includes a piezoceramic, wherein applying a voltage to the piezoceramic results in the valve opening. The self-blocking function, also with a positive pressure at the inlet, and the simple setup are advantages of such a valve. When such a valve is to be combined with a pump in order to avoid free flow, increased space and cost requirements will result due to the separate component required. Additionally, separate piezo-actuation is needed. Furthermore, a zero-level for the piezo/silicon diaphragm must be insured even after the step of gluing the piezoceramic to the silicon diaphragm, even if temperature changes result in a movement of the piezoceramic and silicon diaphragm arrangement. Additionally, such an arrangement would result in a large dead volume between valve and pump, additionally requiring fluidic fittings or connections therebetween.
WO-A1-2004/081390 teaches a double normally closed microvalve the valve outlet of which is coupled fluidically to the inlet of a downstream micropump. The valve is formed in a valve chip which itself has a self-blocking function when a positive pressure is applied to the inlet of the valve which itself has a self-blocking function when a positive pressure is applied to the outlet of the valve, and the valve of which opens when a negative pressure is applied to the outlet. When the pump is switched on, it generates a negative pressure at the pump inlet and the valve outlet, thereby opening the valve. Such a microvalve provides a self-blocking function, comprises passive components so that no piezo actuation is needed, and thus exhibits very good device-to-device reproducibility. Nevertheless, separate components are needed, resulting in additional space and cost requirements. Additionally, such double normally closed microvalves have only been available in silicon, which is expensive. Additionally, when being connected to a micropump, there is a large dead volume and fluidic fittings are needed. In addition, with high inlet pressures, the pump may not generate that negative pressure needed in order to open the valve fluidically connected to the inlet.
WO-A1-2004/081390 teaches a micropump having an integrated double normally closed microvalve. Such a micropump is of a compact design and exhibits a small dead volume. However, only small flow rates can be achieved using micropumps of this kind when the design of the pump is designed for a sufficiently high compression ration. Furthermore, the pump chip needed is large, and with high inlet pressures, the pump may not achieve that negative pressure needed in order to open the integrated double normally closed microvalve.
A medication delivery device comprising a pump and a safety valve at the outlet of the pump is known from WO-A-03/099351. One embodiment of this document teaches a diaphragm pump comprising passive ball check valves at a pump inlet and a pump outlet. A safety valve comprising a valve seat and a diaphragm acting as a valve flap is provided at the pump outlet. An area of this diaphragm is connected to an inlet reservoir of the pump arrangement via a fluidic connection so that a pressure in this inlet reservoir acts on that side of the diaphragm. The other surface of the diaphragm is connected to the pressure generated in a pump chamber of the pump via the check valve at the outlet of the pump.
In accordance with WO-A-03/099351, when the pump is switched off, the safety valve is pressure-balanced over nearly the entire size of the diaphragm, but not in the region inside the safety valve seat. The advantage of a safety valve connected in series to the outlet of a micropump is that a positive pressure at the pump inlet has a closing effect on the safety valve. When the pump is in operation, a relatively small positive pressure generated at the pump outlet can open the safety valve. The pump arrangements described in WO-A-03/099351, however, are of disadvantage in that separate components are needed, which in turn results in increased space and cost requirements. Additionally, the pump arrangements exhibit a large dead volume, wherein again fluidic fittings are needed.
Consequently, there is demand for a pump arrangement in which free flow can be prevented in an unactivated state and which comprises a simple setup and provides a small dead volume.